Pneumatic level switches can measure which of the following?

Pneumatic level switches are specifically designed to measure the level of liquids or certain bulk materials within a vessel. They operate based on the principles of pressurized air, which translates changes in liquid level into a corresponding pneumatic signal.

In this context, the ability to measure flow, while not their primary function, can relate to applications where the flow rate correlates with the liquid level. When liquid levels change, it can affect the flow rate in a system, such as when monitoring the flow out of a tank where the level is dropping. Therefore, while this can imply some degree of level measurement in a dynamic system, it is essential to highlight that pneumatic level switches are more directly focused on level rather than calculating flow in a conventional sense.

The other choices are not suitable for pneumatic level switches. Velocity pertains to the speed of a fluid and is typically measured using flow meters, not level switches. Distance is a general term that could relate to various forms of measurement, not specifically to level measurement technologies like pneumatic switches. Lastly, humidity is a measurement of the moisture content in the air, typically handled by hygrometers, not pneumatic level technology.

Hence, the correct answer focuses on a niche aspect of how level switches can conceptually relate to flow in